[Nasm-users] From Gas to Nasm

[Paul P. <ppr...@gm...>]

Hello All,

I'm a newbie at Nasm and trying to get my chops wet.  In fact my asm isn't
stellar at all, but trying to learn it as a hobbyist.  I've decided to start
off with a very simple subroutine, attempting to get that working first but
I'm running into lots of problems.  I was able to write my function in Gnu's
Assembler which worked fine, however I don't like it's syntax, hence the
reason for attempting to write it in Nasm which I like better.  The c
library function I am attempting to mimic is bzero.  In short it's  "void
bzero(char *addr, unsigned int len)".  I would have thought this would be
quite easy but alas.

###############################
section .text
global bzero
          ; void bzero(char *s, unsigned int len);

bzero:
        enter 0, 0
.loop:
        cmp [esp + 12], 0                        ; If length is zero
        je .done                                       ;     we are done
        mov eax, [ebp + 8]                     ; Move address of pointer
into eax
        mov [eax], 0                                ; 0 out location
referenced in eax
        add [ebp + 8], 1                          ; add 1 to the address
        sub [ebp + 12],  1                        ; subtract 1 from value of
length
        jp .loop                                         ; continue with
loop
.done:
        leave
        ret
###############################

I've tried prefixing the some of the addresses with the keyword 'byte' but
that didn't help much either.  (Ex:  "add byte [ebp + 8], 1")

Also, I'd like to include the Gas example that did work that I'm trying to
convert into Nasm style syntax.
###############################
bzero:
        pushl   %ebp
        movl    %esp, %ebp
.loop:
        cmpl    $0, 12(%ebp)
        je      .done
        movl    8(%ebp), %eax
        movb    $0, (%eax)
        addl    $1, 8(%ebp)
        subl    $1, 12(%ebp)
        jmp .loop
.done:
       popl    %ebp
        ret
###############################

If this is the wrong list, I apologize in advance and would like an
appropriate pointer to the correct list.

Thanks,
-- 
Paul
__________________

:(){ :|:& };: